Whilst the former science teacher was accused of having sex with the pupil on 2 August 2015, details only emerged seven months later, when a second pupil attempted to blackmail her.
Physics teacher Eleanor Wilson, 28, has been banned from teaching indefinitely after her encounter with the boy on the way back from a visit to the Large Hadron Collider in Geneva.
The alleged incident came to light when another pupil found out what had happened and insisted that Miss Wilson have sex with him too or he would expose her.
"She never had anything to drink on the plane, nothing went on".
However, Ms Wilson's disciplinary panel concluded that Pupil A had been a credible and reliable witness, finding her guilty of unacceptable professional conduct and bringing the profession into disrepute.
She later confirmed in a letter dated May 2016 that she knew that contacting Pupil A in the way that she did was inappropriate and stated that "as the teacher in this situation it was my responsibility to be truthful and I wasn't 100 per cent in my interview with [the school]".
It also said she had tried to cover up the relationship, which continued after the school trip. His emails were reported to the school and police.
"She mutually left the school but nothing sexually happened with the student and for it to come out that it was on the plane was a bit weird really".
The panel banned Wilson from teaching indefinitely in any school and ordered she can not apply to a teaching job.More news: Senate Republican plan to repeal, replace Obamacare fails to get enough votes
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After returning from Switzerland, she told a school newsletter: "The trip will provide a real source of inspiration for our young people as they continue with their studies and think about their future career paths".
But since no evidence came to light, there was nothing the school could do, the report said.
But The Bristol Post on Thursday said police were now looking into the allegations.
The panel heard that she did have a previously good history and was highly regarded as a teacher.
A spokesman for the school - which is not being identified - yesterday (Thurs) condemned Wilson.
Making the announcement on behalf of the Secretary of State, Alan Meyrick said: "Wilson is prohibited from teaching indefinitely and can not teach in any school, sixth form college, relevant youth accommodation or children's home in England".
'We then referred the case to the National College, who have prohibited her from teaching permanently.
An NSPCC spokesman said: "As a teacher, Wilson was trusted by parents, her school and the local community to prioritise pupils' welfare and wellbeing, but instead she abused this trust for her own sexual gratification".
But despite the head teacher hearing the allegations of her conduct no action was taken as there was no corroborating evidence. We welcome this decision.